On Wed, 2012-05-30 at 16:33 +0200, Steffen Rumler wrote:
> Hi,
>
> The system crashes inside the return of the init entry point of the kernel
> module.
>
> I've found the following root cause:
>
> (6) Unfortunately, the trampoline code (do_plt_call()) is using register
> r11 to setup the jump.
> It looks like the prologue and epilogue are using also the
> register r11, in order to point to the previous stack frame.
> This is a conflict !!! The trampoline code is damaging the content
> of r11.
Hi Steffen,
Great bug report!
I can't quite work out what the standards say, the versions I'm looking
at are probably old anyway.
Have you tried the obvious fix?
cheers
diff --git a/arch/powerpc/kernel/module_32.c b/arch/powerpc/kernel/module_32.c
index 0b6d796..989d79a 100644
--- a/arch/powerpc/kernel/module_32.c
+++ b/arch/powerpc/kernel/module_32.c
@@ -205,9 +205,9 @@ static uint32_t do_plt_call(void *location,
}
/* Stolen from Paul Mackerras as well... */
- entry->jump[0] = 0x3d600000+((val+0x8000)>>16); /* lis r11,sym@ha */
- entry->jump[1] = 0x396b0000 + (val&0xffff); /* addi r11,r11,sym@l*/
- entry->jump[2] = 0x7d6903a6; /* mtctr r11 */
+ entry->jump[0] = 0x3d800000+((val+0x8000)>>16); /* lis r12,sym@ha */
+ entry->jump[1] = 0x398c0000 + (val&0xffff); /* addi r12,r12,sym@l*/
+ entry->jump[2] = 0x7d8903a6; /* mtctr r12 */
entry->jump[3] = 0x4e800420; /* bctr */
DEBUGP("Initialized plt for 0x%x at %p\n", val, entry);
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